Backing up NAS

I am trying to backup data on NAS and it has no ndmp capability. I was able to create User Defined selection in BE, choose the appropriate credentials (username and password), and was able to select the folders to backup in NAS to backup. But when I ran the actual backup job itself, it errored out with the message: "e0009b61 - The logon account that was provided does not have valid credentials. Ensure that the user name and password are correct, and then try again."